Mechanism for preventing overloading



' Feb. 24, 1942.

w. J. MILLER ETAL MECHANISM FOR PREVENTING OIVERLOADING Filed March 30, 1939 .7 INVENTOR. WILL/AM J. MILLER ASHLEXJREEK Patented Feb. 24, 1942 um-rep STATES PATENT ore-Ice RECH'ANISM FOR PR EVENTING OVERLOADIN G William J. Miller, ,Swissvale, and Ashley QJJRleek. .Carrlick, Ra.,;.said ,Reek assignoritosaidMiller,

Application *March 30, 193.9, finial Nn.:2fi4;-230

.14,Claims. (own-"15.0)

" plied to machineryfor doing work other than making pottery.

In an automatic pottery machine, the same as in other classes of "industrial machinery, if something occurs to jam the driven-mechanism the resistance to the drive increases as well as the foot pounds of pressure applied-by the drive mechanism and damage usually results.

The vobject of this invention'is ,toprotect the machinery against damage'by stopping itautomatically when any rise .occurs "in-the varying foot pounds of pressure (torque) exerted against the driven mechanism during .a cycle due to a rise in resistance beyond that previously 'predetermined regardless of the source of such increase. I

In carrying out the object of this invention, we provide means, for varying the applied pounds of torque in synchronism with the resistance'for successive cycles having the same or a different set of resistance changes .and furthermore, we

utilize the. driving torque .toeffect a ,discontin u ofthe dividedseat 1 into .co-ioperation with the ation of the driveand apositivevand immediate stopping of the driven parts when a predetermined overload occurs.

In the drawing, Fig. ,1 .is an elevation partly in section showing my improved power transmission and control ,mechanismincorporated in an automatic pottery fabricating machine.

Fig. 2 is a fragmentary view showing the latching *member for the clutch. control. operating instrumentality and certain adjustment .provisions.

Fig.3'is a fragmentary view showing the chuck :spi'ndle clutch and operatingmechanism in one position of reciprocation, the other position 'of reciprocation being shown in Fig. 1.

Fig. 4 is a diagrammaticviewof a recording torquometer.

The machine shownein Fig. lais 1 aapottery fabricating apparatus'i'used .tfor rma-king plates, cups,

of Ware. shown with alternate profile and .die ortheentire setup may "consist of 'dies of different-configuramaterial iby pressing, pressing and jiggering, ;.0r iiggering. The .ware is-=formedin mo1ds}M-which may be charged-with vclayfanid placed on and removed; from the chuck I manually or. mechanically. For aldisclosure of how this may be done mechanicallynreference may be .had to William .J. :Miller7s (British ZPatent #471,589.

Mounted on :theirame 2 of the :machine:is.a camshaft 1.3 with a .cam 94 .Lkeyed thereon for .elevating .crossheadifi to thereby lift the moldtMout fabricating tool :which may be a profile fl :or a die :9. Aaprofile or die ist mounted'oneach-nuadrant 'of the rotatable -turret l 0, said turrethbeing rotated upon the rise of the I crossheadifi: by means of push-rod l dogilland ratchet H. ThBq Ob- ,ject of this :arrangement '3 is to enable production diversification -'from pressed to j iggered .wa-re or for diverse forms of e'ithericlassi in succession or the iperf-ormance'in :succession ofboth the-operaa-tions of pressing and profiling on a single piece Thus, the arrangement may be as tion,- or. profiles.

LWhenut is desired not to'diversify production,

"thedOgiI-Z :mayfbe'thrown outror the push-rod H disconnected and ailocking pin I4 inserted fill :one of the indexing openings I 5 .to hold :the turret --stationary.

In jiggeri-ng, the moldjs rotated relative to the profile in w order to 3 remove :excess 1 material "and smooth the ware surface. .Thetmold may'a'lso be rotated relative to 1 the die whenpressing i or :it may remain stationary, in which ,case :the .drive rbeltil 6 is removed :from the-drive pulleyfl-slidingly keyed on worm shaft '26 :and the driven chuck spindle pulley I8 and the stop .bar l9 unbolted and removed :from the .machine frame. This permitsspringilflseated in boss 2- I to. maintain thrustgon pin :22 (ZseeJFig. 3) thereby forcing pivoted clutch-lever Z3 upitoholdrthe driven disc 25 on iigger spindle l-8,zagainstthestationary braking ,disc .-2:! constantly.

Normally, :as: the ;crosshead rises, pin -22 :abuts agamstbar I 9 :and spring 32 0 :is compressed as the crosshead: approacheszpeak elevation by' shoulder .28 whilst lever 23 comes up against spring 29 and-1s depressed thereby, thus engaging disc 25 with drive disc 30 and rotating the chuckspindle and chuck. When the rcrosshead lowers, spring 20 applies thrust-to pin :22 :and elevates the-same (Fig. :3) fthereby forcing lever 52.3.1 apply-the saucersan'd kindredqarticles"fromzplastic ceramic t5 'lorake as iafOIBSald so that t rotation Urine 1 59 and chain 60. -contoured for applying correct predetermined variable disengagement restraining pressure on mold may be arrested before it is deposited on the seat I.

The mechanism for transmitting power to the cam shaft 3 comprises a gear 3| and worm 32 mounted on worm shaft 26. A clutch is mounted on the lower end of the worm shaft and comprises a drive pulley 34 freely rotatable on shaft 26 and connected to a suitable source of power by belt 35. A friction disc 36 is keyed on shaft 26 and is faced on top and bottom surfaces with friction rings 31 for driving engagement with the drive pulley 34 and a braking disc 38 respectively, which is secured to the machine frame by studs 39.

The clutch is engaged by raising the shaft 26 vertically by means of a bifurcated lever fulcrumed at 4| on the machine frame. The lever pivotally on trunnions 4la supports a floating cartridge bearing 42, vertically positioned on theshaft 26 by collars 43. When the handle is lowered, the clutch is disengaged and the brake set to thereby stop the rotation of shaft 26 as well as the motion of the driven parts.

To hold the lever 40 in clutch engaging position, it is provided with an extension 44 having roller 45 mounted at the end thereof for coheld against roller 45 by an adjustable tension spring secured to one arm of bellcrank 5| pivotally mounted on stub shaft 52, the other arm having a roller 53 which engages cam 54 mounted on jack shaft 55.

Jack shaft 55 is driven in synchronism with cam shaft 3 by sprockets 58 and Cam 54 periphery is suitably the latch 46 through tension control of spring 5|].

Owing to the raising and lowering of the crosshead, the starting and stopping of the chuck drive and the pressure required to press the clay under the die, the foot pounds of resistance to the drive fluctuates considerably during a machine. cycle. Co-incidently, the foot pounds of torque delivered to drive the mechanism varies. Thus, at a low load period when delicate apparatus are functioning, a very slight overload will be provided to stop the machine and avoid breakage of apparatus, whereas, without this variable feature the peak torque would be applied. Thus, each revolution of shaft 3 provides a certain set of changes in resistance or torque requirements, and the value and instant of occurrence ascertained by instrumentation or calculation but preferably by a recording torquometer. (See Fig. 4.)

The preferred method of laying out the periphery of cam 54 is to mount a cam blank 60 on shaft 55 with one side Surface chalked and to then locate the stylus 6| of the torquometer, Fig. 4, on are AB midway between the centers of of shaft 55 and roller 53 positioned at the cam periphery with the scribe bar 62 radial to the arc.

Belt 35 goes over floating roller 6'! and under fixed roller 63 and when the drive is clutched in, the scribe bar is oscillated by frame 64, link 65 and compression spring 66 in response to variations in torque as transposed into variations in pull on the lower run of belt 35. The throw of the scribe bar may be varied by repositioning link 65. It is understood that the machine is operated under normal operating pressures when the re- 75 cording is made. When shaft 55 has made one complete revolution, the blank is removed and the cam periphery machined to the line scribed thereon.

When successive cycles have similar torque phases and values, the cam 54 preferably is rotated at the same speed as cam sh'aft 3. However, when succeeding cycles have dissimilar characteristics then the ratio of cam rotation to that of shaft 3 rotation and various sets of cam contours formed on cam 54 should coincide, to always apply a predetermined limit of excess torque and when this is exceeded, the excess axial pressure applied by the worm 32 to gear 3| disengages latch 46 from lever 44, thereby disengaging the clutch 36, gear 3| ceases rotating and the worm through momentum will screw shaft 26 and disc 36 down against brake disc 38 thereby preventing further movement of the driven mechanism through momentum. Meantime roller 45 snaps into the upper notch 56 of the latch and locks the operating handle against displacement until the trouble is cleared.

One advantage of this invention is that the driven machinery is instantaneously stopped before any damage to operating parts can occur upon an abnormal rise in operating pressures. This is exceptionally advantageous in the case of pottery machinery wherein a crushed or broken mold may occasion several minutes delay cleaning the fragments out of the chuck and other parts of the mechanism with consequent loss of production during the interval. Pottery molds are made of plaster and have little or no bendin movement and they burst if loaded sufficiently in pressure, particularly if the pressure is localized.

The invention is applicable to a wide variety of industrial machinery having power characteristics comparable to those of the machine illustrated. For instance, the invention could be applied to a lathe and a number of interchangeable cams provided to control the torque application in accordance with the requirements of the work.

It is to be understood that the structure herein shown has been selected for the purpose of illustration or example and, that various changes in size, shape and arrangement of parts may be made without departing from the spirit of the invention or the scope of the appended claims.

Having thus described our invention, what we claim is:

1. In apparatus of the class described, a driven mechanism, a drive mechanism therefor, a clutch for releasably coupling said driven and said drive mechanisms together and means for varying the torque transmitting ability of the clutch whilst the driving connection subsists including a cam having a working surface developed according .to the normal resistance changes imposed by the driven mechanism on the drive during an operations cycle.

2. In apparatus of the class specified, a driven mechanism, a drive mechanism, a clutch for releasably coupling said driven and said drive mechanism together, means for varying the torque transmitting ability of the clutch whilst the driving connection subsists including a cam having a working surface developed according to the normal resistance changes imposed by the driven mechanism on the drive mechanism during a succession of operations cycles.

mechanism having variations-in the foot pounds of resistance during a cycle and means including a cam for effecting changes in torque applied by the driving mechanism conforming to the instant and amount of change in the normal resistance of the driven mechanism whereby fluctuations in resistance will be compensated for by fluctuations in torque to a previously predeter mined and required amount and means operable in response to a deviation therefrom for discontinuing the application of torque to the driven mechanism.

4. In a machine wherein the driven mechanism operates in successive cycles, mechanism for automatic-ally discontinuing the drive in response to deviations in resistance from that normally imposed on the drive mechanism thereby which comprises, a releasable means for discontinuing the drive and means for imposing a restraining pressure thereon including a cam having a working surface developed in accordance with the resistance changes imposed by the driven mechanism in one or more cycles.

5. In apparatus of the class described, a cam shaft, a cam mounted on said cam shaft for actuating machine components, an endwise displaceable worm shaft for driving said cam shaft, a clutch for said worm shaft, means for engaging and disengaging said clutch, mechanism for locking said means in clutch engaging position by preventing endwise displacement of said worm shaft, said means comprising a latching mechanism on which the pressure is varied as the working torque is varied on the cam shaft and means for transmitting pressure from said cam shaft to said latching mechanism including a cam having a working surface developed in accordance with the variations in Working torque imposed on the cam shaft a pivoted lever and a resilient member connecting said lever to said latching mechanism.

6. In apparatus of'the class described, a driven mechanism, a cam shaft, a cam mounted on said shaft for actuating said driven mechanism, a clutch and a brake, an endwise displaceable drive shaft for actuating said cam shaft, means for engaging and disengaging said clutch which includes an operating handle connected to said drive shaft for raising and lowering the same, a latch member adapted to co-operate with one end of said handle, resilient means for imposing a restraining pressure on said latch member for retaining the latch member in latched position and means for varying the tension on said resilient member comprising a lever and a cam having a working surface developed in accordance with the changes in torque imposed by the driven mechanism on the drive, said latch member being adapted to yield in response to a deviation in torque from that applied to meet the normal resistance of the driven mechanism to disengage said clutch and set said brake.

7. In apparatus of the class described, a driven mechanism, a drive shaft therefor, a

v clutch, means for engaging and disengaging said clutch and releasable means for locking said clutch in engaged position including a latch member, a restraining means therefor and means for varying the restraining pressure imposed on said latch member comprising, a cam mounted for rotation in unison with said driven shaft, said cam having a surface developed substantially in accordance with the torque changes imposed on the drive shaft by said driven mechanism.

, the driven mechanism.

9. In apparatus of the class described, in combination, a driven mechanism, a drive mechanism, a clutch automatically disengageable when the resistance to the working torque becomes excessive and means which automatically varies the value of the torque at which the clutch disengages.

10. In apparatus of the class described, in combination, a driven mechanism, a, drive mechanism, a clutch for coupling said mechanisms together automatically disengageable when the resistance to the working torque becomes excessive, a brake assembly automatically engageable when the clutch is disengaged for holding the driven mechanism stationary and means which automatically varies, during the cycle of operations of the driven mechanism, the value of the torque at which the clutch may disengage and the brake engage.

11. In combination with apparatus for the manufacture of pottery Ware, the combination which comprises a driven mechanism, a drive mechanism, a clutch for coupling said mechanism together automatically disengageable when the resistance to the working torque becomes excessive and means which automatically varies the value of the working torque at which the clutch may disengage during the cycle of operations of the driven mechanism.

12. In apparatus of the class described, in combination, a driven mechanism, a drive mechanism, a clutch for coupling said mechanisms together automatically disengageable when the resistance to the working torque becomes excessive and means which automatically varies the value of the torque at which the clutch disengages including a cam having a working sur face developed in accordance with the resistance changes imposed by the driven mechanism on the drive mechanism during a cycle of operations.

13. In apparatus of the class described, in combination, a driven mechanism, a drive mechanism, a clutch for coupling said mechanisms together automatically disengageable when the resistanceto the torque transmitting ability of the clutch becomes excessive and means which automatically increases and decreases the value of the torque transmitting ability of the clutch and the value of the torque at which the clutch may disengage.

14. In apparatus of the class described, in combination, a driven mechanism, a drive mechanism, a clutch for coupling said mechanism together automatically disengageable when the resistance to the working torque becomes excessive and means which automatically varies the value of the torque at which the clutch may disengage and the torque transmitting ability of the clutch 

